h1 = {
    'a'=>'One',
    'b'=>'Two',
    'c'=>'Three',
    'd'=>'Four'
}
p(h1)
print "--------------------------------------------------------------------------------------------------\n"
$continue
begin
  $continue = ''
  print "[Ban nhap key can seach]\n"
  key = gets.to_s.chomp
  if h1[key]!=nil
    p(h1[key])
  else
    print "[Co so du lieu ko ton tai tu khoa, ban them dinh nghia tu khoa do]\n"
    value = gets.to_s.chomp
    h1.store(key,value)
  end
  print "[Ban co muon tiep tuc khong [yes/no]]:\n"
  $continue = gets.to_s.chomp

end until $continue == 'no'